My Design - Trifoglio 25' - Suggestions & Opinions

Discussion in 'Sailboats' started by DVV, Nov 20, 2020.

  1. DVV
    Joined: Nov 2020
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    DVV Junior Member

    It looks better, thats true.
    Yes the part in the water is the blue one. I attach a pic with the waterline also imposed.
    I will post a pic of the heeled vessel.
    In a chop, helled, she will show the 'middle' flat area to the water. But, it is not very wide, it should be between 10 and 15 cm (4-6inch), I thought this would be enough not to pound to much.
    I will loose some performance upwind, and a little form stability, but I guess chop and little wind when closewinded is just a situation a which a scow will never be a its top. I am willing to accept this to obtain other qualities.
    The point is do have a bow high enough and that shrinks enough also transversally not to suffer to much of it. When I increased the height of the bow, I also made it a little smaller, in increase this effect. With an image of the heeled vessel hopefully it will be easier Schermata 2020-12-08 alle 19.20.53.png
     
  2. Will Gilmore
    Joined: Aug 2017
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    Will Gilmore Senior Member

    I also like the look of the undercut bow better. I don't see it affecting strength as long as you frame it out.

    You know the calculations, not I, but that displacement looks light to me. I would expect the WL to come up a little higher. If your calculations are good, don't listen to me, I'm not a NA, I'm an artist and a cabinet maker and a chicken, turkey and quail farmer who also keeps bees. On occasion, I dream of sailing.

    -Will (Dragonfly)
     
  3. DVV
    Joined: Nov 2020
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    DVV Junior Member

    'My' calculations are just the ones that the software gives me. I just need to set the correct depth, and I have been able to get this simple task wrong more than one time.
    I teach mat in an highschool, not an expert at all. I love boats, at some point I started wandering exactly how do they work and I studied it as a hobby. And then the game evolved into a design. It took a lot of time, but somehow its there now. And now I want to finish it and build it.

    The hull is quite large, more than it seems from the pic I posted. I attach one from below, in blue the underwater area.

    EDIT: I said something wrong. Thats the weight that comes out from the framing and interiors that I draw, the chosen thickness and the weight for sqm that I set. Tomorrow I will post an illustration of framings and interiors, and then the ply thickness I used for the weight. May be you could see what you think.

    Schermata 2020-12-08 alle 22.35.15.png
     
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  4. DVV
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    DVV Junior Member

    This there are two pictures of the boat heeled 20° with displ 1,8tons ant 2tons. They seem fine, dont you think? Schermata 2020-12-08 alle 23.01.28.png Schermata 2020-12-08 alle 23.05.26.png
     
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  5. Will Gilmore
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    Will Gilmore Senior Member

    I went to school to teach high school math. Quit 2 classes short of my masters. Decided to try building a homestead business instead.

    Your design looks good. I like your approach.

    -Will (Dragonfly)
     
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  6. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    I still think you need to understand the hull dynamics in waves.

    Most of the scow bows I saw in the linked article have less vertical dimension.
     
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  7. Will Gilmore
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    Will Gilmore Senior Member

    I just searched "scow bow sailboat bluewater" and saw mostly racing boats, most with foils.
    upload_2020-12-9_9-20-21.png
    This one has the secondary chine, it looks good. I think it will make for a nice ride. Wakes and chop may be harder, but really, what are you looking for? Racing, cruising, bay sailing are all different experiences. A sudden stopping force will stress the rig, but really, all sailboats should be designed with that possibility. It's the repetitive pounding that's unique.

    -Will (Dragonfly)
     
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  8. DVV
    Joined: Nov 2020
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    DVV Junior Member

    This is a boat for me. No racing planned. Junk rigged.
    I want her to bring me around my usual sailing area. It is thought to be easy to singlehand, and that's what I want to do.
    Just move around, me and her, exploring, enjoying, experimenting.
     
  9. DVV
    Joined: Nov 2020
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    DVV Junior Member

    Tonight I played with shapes again.
    I tried a round bow. Just to see it. I still think its too difficult to build.

    What you guys think?

    Schermata 2020-12-09 alle 22.20.16.png
     
  10. fallguy
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    fallguy Senior Member

    I only meant for the bottom edge to be rounded. I see little benefit in making it round(er) all the way.

    Your change to the extra chine was good. But you ought to challenge the design with varying degrees of chop to see if, no when, she'll hit.

    Are you length limited for a class?
     
  11. DVV
    Joined: Nov 2020
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    DVV Junior Member

    The idea was to round just the bottom edge as you say, but I was not able to explaining it to the software
    I am just playing with shapes at this point, I still think I will stick to the 'double chined bow' design.

    I dont know exactly how to do what you suggest. I can set some wave height and see where they hit the hull, especially when heeled, but - even if, as you said, you go though the water - the bow will also go up on an incoming wave, and down once it passed. So to me it is quite difficult to have proper answers. Am I wrong?

    EDIT: no class limitation, just space and cost. 25feet looks a fine compromise in my eyes
     
  12. fallguy
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    fallguy Senior Member

    Someone here must know, but not me.

    I would tend to think that half the height of a wave impacts the hull. So a wave (not swell) one foot high would have an impact at 6" above the designed waterline. And it would interact more with the second chine up on the modified version.

    The question should go out, as a question.

    The other thing to be mindful of is that scow bow is a sail. And as such, it should be minimized as its effects to wind are not going to be lovely. I think splitting it in half has been done on some of the linked articles; then at least the effects are lessened. But a flat scow as drawn originally would reduce your angle to windward. I am not much of a sailor (none), but I read a lot about boats. Gonzo might comment more. He is the sailor.

    Your last drawing does split the scow into two it appears unless jist an illusion.

    I got my first introduction to sailing in a Gil Gilpatrick designed Laker canoe. The wind picked up and so did the bow and I was blown sideways all the way across the lake as I paddled into the wind. I did not take her back out until she had a small tracking skeg. But you won't have that issue. However, when I first saw your first drawing; I thought about it.
     
  13. Doug Halsey
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    Doug Halsey Senior Member

    ...except for these from post #35 of that thread

    [​IMG]
     
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  14. fallguy
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    fallguy Senior Member

    I was hoping a sailor would comment!

    can we agree those scows are both rather tiny in comparison to the original drawings here and even the modified?

    As a sailor, do you have a concern about the scow surface area as a percent of mainsail for to the wind and the boats ability to windward?

    If, for example, the scow is 9 square feet and the main is 200, then the scow is 4.5% dead to wind. I have been head onto the wind many times in my open skiff and once the wind gets you sideways; it keeps you.
     

  15. DVV
    Joined: Nov 2020
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    DVV Junior Member

    This thing you say its interesting and I did not think about it. Does you skiff have a keel?
     
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